This invention relates generally to structural panels for building construction and is particularly directed to high strength structural insulated panels which are highly resistant to bending or bowing such as caused by exposure to moisture or changes in humidity.
Structural insulated panels are gaining increasing acceptance in building construction in replacing the conventional combination of drywall sheets and rolls of fiberglass insulation. The typical structural insulated panel includes an inner insulating core such as of plastic foam and at least one outer facing comprised of a rigid material such as gypsum or cementous composite, oriented strand board (OSB), or an agricultural board product such as strawboard. While a facing of gypsum or cementous composite is highly resistant to moisture, OSB or an agricultural board product is sensitive to changes in humidity. For example, OSB expands, or swells, when exposed to water or increased humidity. This OSB expansion is irreversible as the OSB does not return to its original size or shape with a return to lower humidities. This causes a bowing, or warping, of the structural insulated panel. If this occurs prior to installation, the structural insulated panel is generally not usable and must be discarded. If this occurs after the structural insulated panel has been installed in a building structure, the panel may develop cracks, become detached from the underlying support structure, or may result in a distorted wall or ceiling structure requiring panel replacement.
The present invention addresses the aforementioned limitations of the prior art by providing a high strength structural insulated panel including an inner insulating core with a gypsum fiberboard facing disposed on a first surface of the insulating core and an OSB facing incorporating a polyisocyanurate or urethane resin disposed on a second opposed surface which renders the panel highly resistant to water and changes in humidity.
Accordingly, it is an object of the present invention to provide a high strength, lightweight structural insulated panel which is highly resistant to fire, insects and the environment, particularly to water and changes in humidity.
It is another object of the present invention to provide a structural insulated panel which can be machined on site and is easily adapted for a particular installation.
It is a further object of the present invention to provide a structural insulated panel for building construction which has high dimensional stability over a wide range of various environmental parameters.
The present invention contemplates an insulated structural panel comprising a generally flat insulating core having first and second opposed generally planar surfaces; a first outer facing attached to the first surface of the insulating core and comprised of oriented strand board incorporating a polyisocyanurate or urethane resin; and a second outer facing attached the second surface of the insulating core and comprised of gypsum fiberboard incorporating fiber reinforcing particles.